The present invention relates to photonics chips and, more specifically, to structures including a waveguide core and methods of fabricating a structure including a waveguide core.
Photonics chips are used in many applications and systems including, but not limited to, data communication systems and data computation systems. A photonics chip integrates optical components, such as waveguides, optical switches, and bends, and electronic components, such as field-effect transistors, into a unified platform. Among other factors, layout area, cost, and operational overhead may be reduced by the integration of both types of components into a photonics chip.
A back-end-of-line (BEOL) interconnect structure may be used to electrically couple device structures fabricated on a substrate during front-end-of-line (FEOL) processing. Photonic modes in narrow waveguides can couple with the radiation modes supported by dielectric layers in the BEOL interconnect structure. The coupling, which may be induced by modal index matching between the narrow waveguide and the BEOL dielectric layers, can dramatically degrade waveguide performance. Silicon nitride waveguides are characterized by smaller effective refractive indices and weaker mode confinement than single-crystal silicon waveguides. Consequently, the unwanted coupling with the BEOL dielectric layers may be especially problematic in connection with narrow silicon nitride waveguides, such as tapered sections of silicon nitride waveguides.
Improved structures including a waveguide core and methods of fabricating a structure including a waveguide core are needed.